It's the prep school and college educations. The elite used to be Republicans. Now they are leftists. Prep schools used to be conservative and Christian (Episcopalian). Now they are all politically correct.
Before the 70s, most of the rich people from "good" families whom I used to know were Republicans, at least of the country club sort. Now almost all of them are liberals.
When I saw all the Kerry bumper stickers at the yacht club this summer, all I could think was "Rich People For Kerry."
We even have a bit of what you describe down here in Nashville....very wealthy preppie southern wasps who are libs....most belong to some sort of apostate prod church.
Wealthy southern jews tend to be libs too although at a slightly lower rate than in the NE...
Thankfully, most non minority types here are at least 65% conservative...in the Deep South it's even higher....maybe in the 80% range.
I think a lot has to do with perspectives and realities...on things like social issues and such hot buttons as abortion and racial programs and gun rights. The rubber meets the road on that stuff down here.